The present invention relates to an improved method of progressively and horizontally casting lightweight sandwich panels to create house wall panels.
Conventional house construction traditionally consists of obtaining many small components from many sources and physically assembling these many components in a predetermined sequence, usually out in the prevailing weather conditions with skills of many different tradesmen divided up into many sub-contracts. Supervision is infrequent, consequently the quality of the finished house is largely determined by the skills and integrity of each of the tradesmen. These are very inefficient methods of assembling any product, especially products as expensive and complex as large housing projects.
The selection of house construction materials has evolved slowly and usually combines the least expensive acceptable materials with the skills of available tradesmen. The building industry has focused on establishing standards for each component, for example framing lumber, siding, insulation, The size of each of these components is standardized in order to control costs and reduce waste.
There is a great need to for a simple method of combining all of these components into one product and manufacturing this product on a mass production basis, creating houses that are more durable, much easier to assemble, yet retain the appearance of a typical house.
One such invention, U.S. Pat. No. 5,697,189 granted to John and Andrew Miller on Dec. 16 1997 describes a wall suitable for casting in a mass production process.
This specific patent discloses a type of cementitious wall with blocks of insulative material each completely surrounded by a monolithically poured cementitious material with a continuous upper track and a projecting floor connection means. Other claims include vertical cementitious ribs reinforced with vertical steel reinforcing bars, accurately cast window and door openings. The subsequent assembly of these completed walls on site simplifies house construction
The actual method of assembling and casting this said wall is not described in detail, however anyone skilled in the art of creating very thin cementitious skins on a large sandwich wall panel, with a central core of expanded polystyrene, will realize the necessity to progressively cast this wall in a horizontal position. The first thin skin is applied evenly to a horizontal form tray, then an assembly of expanded polystyrene panels and steel reinforcing is applied to this first fluid cementitious skin, followed by the application of second fluid cementitious skin applied over the upper face. This application of this second cementitious skin includes filling the voids between the expanded polystyrene panels and completely encasing each panel. This second skin also provides a method of bonding both skins together and encasing the steel reinforcing on both faces of the wall. The face of the first skin cast against the form tray reproduces whatever texture is on the face of this form tray. The face of the second exposed skin is mechanically finished with trowels, usually with a smooth finish.
The manufacture of this particular product as described in this existing patent has a number of inherent manufacturing and design problems. The use of monolithically poured cementitious material as a means of connecting both faces of the wall panel together at the vertical ribs. In addition the structural design of the rib necessitates of total encasement of these vertical steel reinforcing elements. More specific details are as follows;
The first disadvantage of this existing patent is the necessity to and inability of ensuring that voids do not occur in the central portion of these ribs. Considerable difficulty is experienced in ensuring that the fiber filled cementitious fluid continuously flows into the narrow joints between blocks of insulative material and upper steel reinforcing bar without creating air pockets. Voids in the rib area greatly impairs the structural integrity of the entire wall panel.
Another disadvantage of this existing patent is the necessity to and inability of ensuring a continuous bond along the wet joint line between the first wet lower skin of the wall panel and the second skin the cementitious fluid designed to flow between the blocks of insulation and bond both sides of the panel together with cementitious fluid. Failure to continuously bond both sides of the panel together in this rib area also greatly impairs the structural integrity of the entire wall panel.
Another disadvantage is the reliance on the tensile strength of the fibers in the cementitious rib area providing the only tensile connection between the steel reinforcing bars on either face of the panel. It was not possible to achieve the full potential of the strength of the steel reinforcing bars in solid ribs and the strength of the fibers proved to be inconsistent
Another disadvantage is that the wall as described in this existing patent is limited in its application to single level houses with solid concrete floors, cast on the ground. There is no connection provision for walls for upper floors and no provision for floors above ground or between floors for any other type of construction.
Another disadvantage is that the projecting connecting bars at the bottom of the wall protrude beyond the wall face, creating difficulties in the manufacturing process and difficulties with temporary storage when panels are stacked against each other.
Another disadvantage is the method of obtaining a smooth finish on the upper face of the second skin of cementitious fluid. It is necessary to this wait for the surface of the second skin of the cementitious material to partially solidify and then repeatedly trowel this surface as it hardens. The timing of this solidifying process is unpredictable and the finishing procedure is a time consuming process, not suitable for an industrial process. The trowelled upper surface results in an undulating imperfect surface, in contrast to the precision of the face of the first skin cast down against the surface of the form tray.
The primary object of this invention is to eliminate the foregoing manufacturing and structural flaws found in this prior patent, and although this present invention retains the external appearance of the wall as described in the prior patent, the method of manufacture and the technical description of this new invention is very different.
One improvement to the prior patent is the use of a vertical welded steel truss in the vertical ribs between the edges of the beveled insulation blocks that replaces the individual vertical steel reinforcing bars on either face of the wall. These rib trusses are constructed out of small diameter deformed steel chords, electrically welded to interconnecting small diameter steel diagonal bracing members. These trusses are ultimately provided with lateral stiffness by both locally thickened cementitious skins, with the truss ends restrained in solid cementitious material at the top and bottom of the wall. Both chords of these trusses initially remain fully exposed and are subsequently encased with the cementitious fluid.
Another improvement to the prior patent is the use of the many interconnecting diagonal bracing members of the vertical trusses as the means of connecting both independent skins of the wall together. The small diameter steel diagonal bracing members of these trusses are sandwiched between the sides of the beveled blocks of insulation. This eliminates the use of wet cementitious material of the second skin to bond to the wet face of the first skin and the use of the fiber in the cementitious material in the central rib area providing the tensile connection between the steel reinforcing bars on either face of the panel.
Another improvement is encasing the lower chord of these rib trusses with cementitious fluid of the first skin by submersing the face of the subassembly of insulating panels and trusses until the lower chord of the trusses are fully encased in cementitious fluid. This also eliminates the need to encase the reinforcing steel on the lower first face with cementitious fluid from the second skin.
Another improvement is the method of controlling the thickness of the first skin by forcing down this internal subassembly down to a predetermined position, with the excess cementitious fluid being displaced to ends of the insulation panels.
Another improvement is casting the second face of the wall panel by waiting until the first skin has solidified then rotating this entire first assembly into a second wet cementitious skin on a separate casting bed in a similar manner to casting the first skin. This provides an excellent predictable finish to the second skin. This avoids waiting for the surface of the second skin to solidify and eliminates all surface trowelling, greatly improving the quality of this second face of the wall.
Another improvement is providing the bottom of the wall with an temporary aligning and connecting device that ultimately provides a permanent connection to the structure below this wall, that does not protrude beyond the wall face, so that walls can be temporarily stacked against each other during handling and shipping.
Another improvement is providing the top of the wall with recesses to accommodate the permanent attachments to the top of this wall, including floors above ground level, second floors, walls on walls, and roof structures including preassembled roofs. A continuous track to accommodate temporary handling devices and other permanent connections is desirable but not essential.
During the making and testing experimental panels it was discovered that it was not necessary to encase the diagonal bracing members of the rib trusses in concrete and only necessary to encase the top and bottom chord of these rib trusses in concrete skins. This in turn isolated the cementitious skins on either face of the panel from each other and improved the value of the insulation panels in this wall.
The specific design of this sandwich wall panel is substantially different from the prior art. The panel manufacturing procedure is greatly improved by avoiding the use of cementitious material in the rib area. The cast surface finish on the second wall face is superior. The strength of this panel increased and the weight of this wall panel reduced The casting of separate skins allows the use of different types of cementitious materials, such as fire rated or high impact skin on one or more wall faces.